1. Field of Invention: A method and apparatus based upon a tube stake that embraces and dampens vibrations in a single row of heat exchanger tubes. The stake is U-shaped, comprising two elongated strip portions of a soft V configuration, joined at one end by a connecting clamp, and a plurality of encircling metal tie fasteners.
2. Brief Description of the Prior Art: Tubes are arranged in bundles within heat exchangers and condensers. The array of tubes is prone to sympathetic vibration and movement, as a consequence of temperature increases and as a result of fluid velocity and density changes both inside and outside of the tubes. Such vibrations have an oscillatory nature, and the oscillations can reach critical amplitudes and severely damage the tubes.
This well-known problem has become more critical within condensers or heat exchangers wherein tubes originally comprised of admiralty brass, or other relative stiff materials, are replaced with lighter weight noble metal materials, such as titanium. A Design Guide published by the Heat Exchange Institute, 8th Edition, provides structural standards for different tubing materials, and particularly a maximum mid-span spacing between support plates perpendicular to the center line of rows of tubes. By way of background, a permitted mid-span spacing between support plates typically is on the order of between 30 inches and 50 inches, depending upon the inherent properties of the tube material, and various other design parameters such as pitch between center lines of each tube and the operating conditions of the condenser or heat exchanger.
Tubes primarily are held within tube support plates, at each end and at spaced locations therebetween. Since about 1955, with the advent of multi-spindle drills, a large number of holes typically are drilled at one time, in each tube support plate. The support plates are then spaced longitudinally along the tubes, so as to define several bays. Steam condensers typically are constructed so that the tube support plates space the tubes at apices of an equilateral triangle, with the center line distance between adjacent tubes being equal, in any direction. In that circumstance a tube stake such as that disclosed in WILLIAMS (U.S. Pat. No. 4,648,442) or HAHN (U.S. Pat. No. 4,919,199) can be inserted between lanes of tubes, in order to dampen vibrations through a coaction between adjacent tube rows.
However, due to the design of certain heat exchangers, and particularly at outer peripheries of a tube bundle, it often also is necessary to stabilize a single row of tubes. Where a plurality of tubes in a single row is not adjacent a parallel row of tubes, on at lest one side, it is not possible to stiffen that single row by a conventional tube stake.
It also generally is known that a set of parallel plates, or a U-shaped metal strip member, can be used to clamp around a single row of heat exchanger tubes. NEWTON (U.S. Pat. No. 4,014,314) illustrates a U-shaped clamp with a connector comprising an end piece, that engages the free ends of each connected strip. JABS (U.S. Pat. No. 5,033,542) illustrates a trelliswork that is woven transversely across a row of parallel tubes and then is secured, at each free end, to the frame of a heat exchanger. BIZARD (U.S. Pat. No. 4,702,311) illustrates a flexible, U-shaped pipe that is inserted flat and then inflated to stiffen adjacent rows of tubes. THOMPSON (U.S. Pat. No. 1,430,769) illustrates a single row of transformer coils that are braced between a pair of flat bars, with several bolts interconnecting the flat bars. KOCHEY, Jr. et al. (U.S. Pat. No. 4,013,024) illustrates a slotted band type spacer, wherein weldments and tie rods are used to position flat plates on either side of a row of superheater tubes. NENSTIEL et al (U.S. Pat. No. 5,050,669) illustrates a tube support comprising a pair of parallel plates secured transversely over a set of parallel tubes, and joined by a plurality of staggered pins.